def f(n):
    for i in range(2, n):
        if n%i==0:    return  False
    return True





cif=['zero','one','two','three','four','five','six','seven','eight','nine']
left=[]
right=[]
s=input()
w=s.split()
b=''
for x in w:
    b+=str(cif.index(x))
b=int(b)
for c in range(2,b):
    if f(c):
        left.append(c)
for c in range(b,1500):
    if f(c):
        right.append(c)
if b-max(left) <= min(right)-b:
    print(max(left))
    
else:
    print(min(right))



